A known seat slide device disclosed in JP3114326B has a lower rail, an upper rail, a screw member, a nut member and a covering member. Specifically, the lower rail fixed at a vehicle floor includes an opening portion opening in an upward direction. The upper rail, to which a vehicle seat is maintained, is supported by the lower rail through the opening portion so as to be slidable relative to the lower rail. The screw member is provided between the upper rail and the lower rail so as to extend in a sliding direction of the upper rail. The nut member is fixed to the lower rail and threadedly engaged with the screw member. The covering member fixed at the lower rail includes an upper wall by which the opening portion of the lower rail is covered.
A driving mechanism is connected to the screw member, and the screw member is rotated by a driving force generated at the driving mechanism. In this configuration, the known seat slide device make the upper rail slide relative to the lower rail by rotating the screw member relative to the nut member by use of the driving force generated at the driving mechanism.
According to the known seat slide device, the screw member is positioned above the upper wall of the covering member. In this configuration, because the screw member is positioned between the upper wall of the covering member and an upper wall of the upper rail, it has been considered difficult to set the distance between the upper wall of the upper rail to the upper wall of the covering member to a small value, in other words to set the height of the upper rail to a small value.
A need thus exists to provide a seat slide device in which a height of the upper rail is set to a small value.